Interpretive Summary: Camelina, which is a relative of canola, is being developed as a dedicated biofuel crop for the U.S. Previous work by our Lab has shown that camelina not only grows well in Minnesota, but it can also be grown as a winter annual crop. This means it can be planted in the fall just like a cover crop and then harvested the following summer. Moreover, our previous research showed that fall-planted camelina could be harvested early enough the next summer to allow growing and harvesting a second crop after it. No one has experimented yet with this idea. But, if it is successful, it would provide a way to produce a dedicated biofuel crop and a food crop on the same piece of land in a single growing season. More importantly, this means that a dedicated biofuel crop such as camelina could be produced without sacrificing food security. We conducted a two-year study to look at whether it is agronomically- and economically-feasible to produce soybean, sunflower, and forage millet after harvesting winter camelina, which is referred to as “double-cropping.” The crops planted after camelina were seeded later than they normally would be. However, double-cropped soybean and sunflower yields on average were only 18 to 28% lower than if they were grown as a single crop seeded at a normal time. For the camelina-soybean and camelina-sunflower double-crop, the average combined seed oil yield was 75 gallons/acre and 161 gallons/acre, which is considerably more than if you grew a single crop of soybean or sunflower. Double-cropping is more expensive than producing a single crop. However, our results showed that the camelina-soybean double-crop sequence was both feasible and the most economically attractive. In fact, during the 2009 season, the double-crop camelina-soybean sequence resulted in net earnings of $70 to $142/acre more than if just a single crop of soybean was grown. Furthermore, there was essentially no sacrifice in seed quality of double-cropped soybean and only a small affect on sunflower seed quality over both years of the study. Our research shows that a biofuel and food double-crop system is feasible for the upper Midwest. This research will likely benefit the biofuels industry and useful for growers potentially interested in producing camelina as a dedicated biofuel crop.

Technical Abstract:
Camelina (Camelina sativa L.) is a viable oilseed feedstock for biofuels. Recently, it was shown that fall-seeded winter camelina can be successfully grown in the upper Midwest and may be harvested early enough the following summer to allow producing a second crop. Double-cropping may offer a profitable means of producing a dedicated biofuel crop without jeopardizing food security. To our knowledge no published information exists on exploring double-cropping with winter camelina. Therefore, a 2-yr field study was conducted between 2007 and 2009 in west central Minnesota to evaluate the agronomic and economic viability of producing short-season cultivars of soybean [Glycine max (L.) Merr.], oilseed sunflower (Helianthus annuus L.), and forage millet (Setaria italic L.) after winter camelina in conventionally-tilled and no-tilled soil. In most instances, yields of camelina and the second crop in the double-crop sequence differed between years but not by tillage practice. Averaged over both years, total oil yields for the camelina-soybean and camelina-sunflower sequences were 704 and 1508 L ha-1. Compared to conventionally produced mono-crops, on average, double-crop soybean and sunflower yielded 82% and 72% of their mono-cropped counterparts, respectively. As expected, double-crop production costs were greater than for conventional mono-crops. However, in 2009 if camelina prices were similar to canola, net returns for double-crop camelina and soybean were $172-352 ha-1 higher than for soybean alone with highest double-crop net returns for conventional tillage. Furthermore, double-crop soybean seed protein content was little affected by late seeding, while double-crop sunflower oil content averaged over both years was about 13% lower than conventional sunflower sown at an optimum time. A winter camelina-food or –forage crop double-cropping system may be viable for the upper Midwest USA.